Immunologically modified carbon nanotubes for cancer treatment

ABSTRACT

A method for constructing a compound of immunologically modified nanotubes and method for using the compound to deliver immunoadjuvants to tumor cells and to produce targeted, synergistic photophysical and immunological reactions for cancer treatment. To prepare the immunologically modified nanotubes, carbon nanotubes are dissolved in a solution of glycated chitosan, an immunostimulant, hence using glycated chitosan as a surfactant for rendering the aqueous solution of nanotubes stable. The compound can be used for treatment of cancer. The method includes steps of intratumorally administering immunologically modified nanotubes and administering laser irradiation of the target tumor. The nanotube serves as a carrier to deliver immunoadjuvants to the tumor cells and serves as a light-absorbing agent in a cell body of a tumor in a host. Upon laser irradiation of target tumor cells, immunologically modified nanotubes inside the tumor cells can produce spatially and temporally synchronized photothermal and immunological reactions for cancer treatment.

FIELD OF THE INVENTION

This invention is related to the field of biomedical applications ofnanotechnology. More particularly, the invention is related to a newcompound of immunologically modified carbon nanotubes and the use of thecompound for delivering immunoadjuvants to tumor cells and for producingtargeted, synergistic photophysical and immunological reactions forcancer treatment.

BACKGROUND OF THE INVENTION

Nanotechnology has been used in the biomedical fields. Specifically,single-walled carbon nanotubes (SWNTs) have been applied in variousbiological systems. One intrinsic property of SWNTs is their ability tocross cellular membranes without eliciting cytotoxicity. Anotherintrinsic property of SWNTs is their strong optical absorbance in thenear-infrared (NIR) region. It was reported that SWNTs could enhancethermal destruction of cells during NIR laser irradiation andradiofrequency irradiation. Since biological tissues are relativelytransparent to light in the range of 700-1100 nm, the ideal SWNT forphotothermal therapy should have an absorption band in the NIR region.Furthermore, it is desirable to have nanotubes with uniform size so thata narrow absorption peak can be used for effective optical irradiation.The CoMoCAT method, discussed in “Controlled production of single-wallcarbon nanotubes by catalytic decomposition of CO on bimetallic Co—Mocatalysts” by Kitiyanan B, Alvarez W E, Harwell J H, Resasco D E (2000)in Chem. Phys. Lett. 317:497-503, incorporated herein by reference,produces SWNTs with a narrow and intense absorption band around 980 nm.

For biological applications, SWNTs should be prepared in aqueoussuspension; surfactants are needed for stable dispersion to avoidaggregation of nanotubes. Sodium dodecylbenzene sulfonate (NaDDBS),sodium carboxymethylcellulose (NaCMC), and sodium cholate (NaCholate)are commonly used as surfactants for nanotubes.

The electronic structure of SWNTs is sensitive to changes in thesurrounding electrostatic environment. For example, their opticalresponse can be greatly changed by surface charge transfers or byadsorption of molecules. Therefore, it is crucial to have a SWNTsolution with appropriate optical properties for biomedicalapplications.

Photothermal therapy can be effective for local cancer treatment due tothe sensitivity of tumor cells to temperature elevation. Laserimmunotherapy was developed to combine photothermal reaction withimmunological stimulation to treat metastatic tumors. Its selectivephotothermal effect serves as the first line of assault on the tumor,using a combination of an NIR laser irradiation and a light-absorbingdye. An immunological stimulant is used concurrently to induceimmunological responses. A new compound, glycated chitosan (GC), wasdeveloped as such an immunostimulant. Laser immunotherapy using GC andthe light-absorbing dye has been proven to be highly effective in thetreatment of metastatic tumors in pre-clinical studies. This method hasalso been used to treat late-stage breast cancer patients with promisingoutcomes.

SUMMARY OF THE INVENTION

Anti-tumor immunological response induced by local intervention is idealfor treatment of metastatic tumors. A novel immunologically modifiednanotube system is constructed using glycated chitosan (GC), a potentimmunoadjuvant, as an effective surfactant for single-walled carbonnanotubes (SWNTs). This novel SWNT-GC system has a long-term stabilityand it retains the absorption characteristics of SWNT and theimmunological adjuvant function of GC. Locally administered SWNT-GC andirradiation of near-infrared light produced synergistic, simultaneousphotothermal and immunological reactions in the treatment of tumorcells, both in vitro and in vivo. Laser+SWNT-GC resulted in highlyeffective tumor suppression in animal tumor models, with complete tumorregression and long-term survival in many cases. Tumor-bearing animalssuccessfully treated with Laser+SWNT-GC established total resistance tosubsequent tumor challenges. Passive adoptive immunity transfer usingsplenocytes as immune cells harvested from Laser+SWNT-GC-cured animalsprovided 100% immunity in naive recipients. Laser+SWNT-GC could prove tobe a promising selective local treatment modality that induces systemicanti-tumor response, while minimizing adverse side effects.

To utilize the special absorption properties of the CoMoCAT SWNTs, andto immunologically enhance photothermal effects, a novel SWNT-GC systemwas designed in which GC simultaneously serves as an effectivesurfactant and a potent immunostimulant, providing two crucialfunctionalities to this novel system. SWNT-GC suspension is stable andit completely retains the light absorption characteristics of SWNTs andthe immunological functions of GC. Using local laser+SWNT-GC treatmenthas resulted in significant tumor suppression and anti-tumorimmunological responses in animal tumor models.

Furthermore, nanotubes can enter cells due to their size and electricproperties. Nanotubes can serve as drug carriers. In the method of thisinvention, nanotubes carry the immunoadjuvant, GC, into the tumor cells.Therefore, under irradiation of a laser light of appropriate wavelength,SWNT-GC can produce temporally and spatially synchronized photothermaland immunological reactions in the target tumor cells. The SWNT-GCcombination also has the potential to carry other therapeutic agents totumors so that cancer can be treated with combination therapy of desiredagents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A. Schematic of the immunologically modified nanotube system,SWNT-GC.

FIG. 1B. Absorption spectra of SWNT-GC suspension with different SWNT-GCconcentrations (top curve, SWNT-GC concentration: 135 μg/ml-0.73 wt %;lower curves correspond to consecutive 50% reduction in SWNT-GCconcentration).

FIG. 1C. Raman spectra of SWNT-GC.

FIG. 2A. Selective photothermal effects using SWNT-GC and laserirradiation (thermocouple measurement). Temperature inside gel phantoms(with or without nanotube enhancement) was measured by thermocouplesduring irradiation by a 980-nm laser. The laser power density was 1.13W/cm² and irradiation duration was 5 minutes. The thermocouples wereplaced 4 mm below the sample surfaces.

FIG. 2B. Selective photothermal effects using SWNT-GC and laserirradiation (infrared thermal camera measurement). Temperature increaseon the surface of gel phantoms (with or without nanotube enhancement)was measured during laser irradiations by an infrared thermal camera.The laser power density was 1.13 W/cm² and irradiation duration was 5minutes.

FIG. 3A. Temperature distribution in a gel phantom without nanotubeenhancement before laser irradiation (magnetic resonance thermometrymeasurement).

FIG. 3B. Temperature distribution in a gel phantom without nanotubeenhancement after laser irradiation (magnetic resonance thermometrymeasurement). The sample was irradiated by a 980-nm laser from thebottom. The power density was 0.212 W/cm² with a beam diameter of 3.0cm. This figure shows the temperature distribution 7 minutes after laserradiation.

FIG. 3C. Temperature distribution in a gel phantom with nanotubeenhancement before laser irradiation (magnetic resonance thermometrymeasurement). A nanotube enhanced spherical gel was buried 1 mm belowthe surface.

FIG. 3D. Temperature distribution in a gel phantom with nanotubeenhancement after laser irradiation (magnetic resonance thermometrymeasurement). A nanotube enhanced spherical gel was buried 1 mm belowthe surface. The sample was irradiated by a 980-nm laser from thebottom. The power density was 0.212 W/cm² with a beam diameter of 3.0cm. This figure shows the temperature distribution 7 minutes after laserradiation.

FIG. 4. Subcellular distribution of GC carried by SWNT and transportedinto the tumor cells. The fluorescence images of SWNT-GC-FITC (SWNT-GCconjugated to a fluorescent dye FITC) and GC-FITC (GC conjugated to afluorescent dye FITC) in EMT6 cells were acquired. Cells were incubatedwith SWNT-GC-FITC and GC-FITC for 2 hours, and the fluorescence of FITCfrom cells was detected by laser scanning microscope. Note that GC couldenter cells only when attached to SWNT. Bar=10 μm.

FIG. 5. Viability of in vitro tumor cells under different treatments.Tumor cells were treated with GC (50 μg/ml), SWNT-GC (2.5 μg-50 μg/ml),laser only (60, 120, or 150 J/cm²), or Laser+SWNT-GC (60, 120, or 150J/cm²; 1.25 μg-25 μg/ml or 2.5 μg-50 μg/ml). The treated cells wereincubated in complete medium for 12 hours before assessing cellviability. Bars, means±SD (n=4).

FIG. 6A. In vitro immunological effects of SWNT-GC. TNFα secretion bymurine macrophages incubated with GC or SWNT-GC suspensions, detected byELISA. Macrophages were incubated with GC solution of differentconcentrations (25, 50, and 90 μg/ml, gray bars) or with SWNT-GCsolution of different concentrations (2.5 μg-25 μg, 2.5 μg-50 μg, and2.5 μg-90 μg/ml, black bars) for 24 hours. After incubation,supernatants were collected for the determination of TNFα. Bars,means±SD (n=4).

FIG. 6B. In vitro immunological effects of SWNT-GC: TNFα secretion bymacrophages stimulated by treated EMT6 cells. Macrophages were incubatedfor 24 hours with tumor cells (1:1) treated by GC (50 μg/ml), SWNT-GC(2.5 μg-50 μg/ml), laser light (60-150 J/cm²), or Laser+SWNT-GC (60-150J/cm², 2.5 μg-50 μg/ml). Cells without treatment incubated withmacrophages were used as control. After incubation, supernatants werecollected for the determination of TNFα. Bars, means±SD (n=4).

FIG. 7A. Effects on tumor burden of intratumoral injections (at day 0)of different components: (i) control, (ii) SWNT (1 mg/kg), (iii) GC (25mg/kg), or (iv) SWNT-GC (1 mg-25 mg/kg); 12 mice/group. EMT6 cells wereinjected subcutaneously into the flanks of Balb/c female mice andtreatment took place when tumors reached a size of approximately 300nm³.

FIG. 7B. Effects on tumor burden of intratumoral injections of differentcomponents, followed by laser irradiation (0.75 W/cm² for 10 minutes atday 0): (i) control, (ii) Laser, (iii) Laser+GC (25 mg/kg), (iv)Laser+SWNT (1 mg/kg), or (v) Laser+SWNT-GC (1 mg-25 mg/kg); 12mice/group. EMT6 cells were injected subcutaneously into the flanks ofBalb/c female mice and treatment took place when tumors reached a sizeof approximately 300 mm³. Laser+SWNT-GC and Laser+SWNT weresignificantly more efficacious in tumor reduction as compared with othergroups.

FIG. 8A. In vivo effects of SWNT and GC without laser irradiation:Animal Survival. Survival rates of tumor-bearing mice treated byintratumoral injections (at day 0) of different components: (i) SWNT-GC(1 mg-25 mg/kg), (ii) GC (25 mg/kg), (iii) SWNT (1 mg/kg), or (iv)control: 12 mice/group. EMT6 cells were injected subcutaneously into theflanks of Balb/c female mice and treatment took place when tumorsreached a size of approximately 300 mm³.

FIG. 8B. In vivo effects of SWNT and GC with laser irradiation: AnimalSurvival. Survival rates of tumor-bearing mice treated by intratumoralinjections of different components, followed by laser irradiation (0.75W/cm² for 10 minutes, day 0): (i) Laser+SWNT-GC (1 mg-25 mg·kg), (ii)Laser+SWNT (1 mg/·kg), (iii) Laser+GC (25 mg/kg), (iv) Laser, or (v)control; 12 mice/group. EMT6 cells were injected subcutaneously into theflanks of Balb/c female mice and treatment took place when tumorsreached a size of approximately 300 mm³. Laser+SWNT-GC and Laser+SWNTwere significantly more efficacious in animal survival as compared withother groups.

FIG. 9. Tumor rechallenge of successfully treated mice. Tumor-bearingmice cured by Laser+SWNT-GC or Laser+SWNT treatment were challenged with2×10⁶ viable tumor cells 100 days after the initial inoculation. Naivemice of the same age were also inoculated with 2×10⁶ viable tumor cellsas controls. All the mice cured by Laser+SWNT-GC showed total resistanceto the challenge; however, mice cured by laser+SWNT, while with aprolonged average survival time, were not completely refractory to thetumor rechallenge.

FIG. 10. Adoptive immunity using splenocytes as immune cells. Spleencells from mice successfully treated by Laser+SWNT-GC or Laser+SWNT werecollected as immune cells. Spleen cells from untreated tumor-bearingmice were also used as control immune cells. Viable tumor cells wereadmixed with spleen cells from different mice, then injected into naivemice. The spleen cell to tumor cell ratio was 50,000,000:100,000 permouse. The spleen cells from mice treated by Laser+SWNT-GC completelyinhibited the tumor growth; all the mice in this group survived and nonedeveloped tumors. The spleen cells from Laser+SWNT-cured mice andcontrol mice only provided 30% and 10% protections to the recipients,respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Materials and Methods

CoMoCAT Single-Walled Carbon Nanotubes (SWNTs).

The CoMoCAT SWNT is used due to its unique properties of uniform sizeand NIR light absorption. The CoMoCAT method produces single-walledcarbon nanotubes using a silica supported bimetallic cobalt-molybdatecatalyst. The product is composed of a narrow distribution of nanotubetypes, with an average diameter of 0.81 nm. This type of nanotube hasbeen of interest due to its absorption characteristics in thenear-infrared region, especially as it possesses an intense absorptionband at approximately 980 nm. Nanotubes of this type are discussed in“Carbon nanotube-enhanced thermal destruction of cancer cells in anoninvasive radiofrequency field” by Gannon C J, Cherukuri P, Yakobson BL, Cognet L, Kanzius J S, Kittrell C, Weisman R B, Pasquali M, Schmidt HK, Smalley R E, Curley S A (2007) in Cancer 110:2654-2665, “Multiphotonmicroscopy in life sciences” by König K (2000) in J. Microsc. (Oxford)200:83-104, “Controlled production of single-wall carbon nanotubes bycatalytic decomposition of CO on bimetallic Co—Mo catalysts” byKitiyanan B, Alvarez W E, Harwell J H, Resasco D E (2000) in Chem. Phys.Lett. 317:497-503, and “Narrow (n,m)-distribution of single-walledcarbon nanotubes grown using a solid supported catalyst” by Bachilo S M,Balzano L, Herrera J E, Pompeo F, Resasco D E, Weisman R B (2003) in J.Am. Chem. Soc. 125:11186-11187, each of which is hereby incorporated byreference.

Glycated Chitosan (GC).

GC is used as a special immunoadjuvant and as an effective surfactantfor SWNT in this invention. GC was developed as an immunologicalstimulant for laser immunotherapy to treat metastatic tumors. GC isnontoxic in cell culture and in animal studies, as shown by previousexperiments. GC may be synthesized by incubating an aqueous suspensionof chitosan with a three-fold excess of galactose and subsequentstabilization by borohydride reduction of the mixture of Schiff basesand Amadori products as discussed in “Laser Immunotherapy: A NovelTreatment Modality for Metastatic Tumors” by Chen W R, Carubelli R, LiuH, Nordquist R E (2003) in Mol. Biotechnol. 25:37-43, herebyincorporated by reference. Examples of chitosan-derived biomaterials maybe found in U.S. Pat. No. 5,747,475, the contents of which are herebyincorporated by reference. In addition to its immunoadjuvant properties,the molecular structure of GC makes it a superb surfactant for SWNTs.

Preparation for SWNT-GC and SWNT-PEG Solutions.

CoMoCAT SWNT is used as an example of carbon nanotubes in thisinvention. Other nanostructures, such as nanoparticles, nanoclusters,and nanorods, can be used with GC to construct immunologically modifiednanostructures. To prepare the SWNT-GC solution, pristine CoMoCAT SWNTsof 2.5-2.7 mg were mixed with 7-ml aqueous GC of differentconcentrations. It is contemplated that an amount within any subset ofranges within the range of 1-5 mg will also be effective. To dispersethe SWNTs, the mixture was sonicated for 30 minutes using an ultrasonicprocessor. This suspension of SWNTs was then centrifuged at 30,150 g for30 minutes. The final concentration of SWNT in GC solution wasdetermined by comparing its optical absorbance with that of acalibration SWNT solution of known concentration.

Optical Spectra Measurements.

The optical absorbance of SWNT-GC was measured by a UV-vis absorptionspectrophotometer. To take advantage of the intrinsic optical propertiesof SWNTs, Raman spectroscopy was used to verify the SWNT-GC conjugationusing capillaries without spinning or stirring during the measurements.An argon ion laser (514.5 nm) was used for excitation in combinationwith a 40× objective of a microscope, a spectrometer, and a CCDdetector. After focusing on the center of the capillary, the Ramanspectrum of the sample was recorded with a resolution of 2 cm⁻¹ (10 mWpower, 20 seconds collection time).

Selective Photothermal Effects of Laser+SWNT-GC Using Gel Phantoms.

SWNT with a 978 nm absorption peak was used for the SWNT-GC suspension.Gel phantom was mixed with SWNT-GC suspension to simulateabsorption-enhanced targets. A 980-nm laser was used to irradiate bothSWNT-GC gel samples and normal gel samples. Temperature increases at adepth of 4 mm below the gel surface was measured by thermocouples. Thesurface temperatures of gel phantoms with and without SWNT-GCenhancement during laser irradiation were measured using an infraredthermal camera.

Using a magnetic resonance imager, the temperature distribution inside agel phantom during laser irradiation was measured. The gelatin gel wasplaced in a cylinder container. The temperature distributions inside anormal gel block, before and during laser irradiation were alsomeasured. To enhance the gel absorption, a gel sphere of 0.5-cm radiuscontaining SWNT-GC suspension was imbedded in the gel 1 mm beneath thesurface to simulate a deep target tumor. The temperature distributioninside the SWNT-GC enhanced gel block, before and during laserirradiation, were measured.

Cell Culture.

Murine mammary tumor line EMT6 cells and murine macrophage line RAW264.7cells were used in the experiments. The cells were cultured in RPMI 1640(GIBCO) supplemented with 15% fetal calf serum (FCS), penicillin (100units/ml), and streptomycin (100 μg/ml) in 5% CO₂, 95% air at 37° C. inan humidified incubator.

GC-FITC and SWNT-GC-FITC Functionalization.

FITC (13 mM, 50 μl) was dissolved in DMSO, and then mixed with 1 ml GCor SWNT-GC solutions. After incubating the mixture for overnight at roomtemperature, avoiding light exposure, the GC-FITC or SWNT-GC-FITCsolutions were filtrated through 100 KDa filters (Millipore) to removeexcess FITC. Then GC-FITC and SWNT-GC-FITC were incubated with EMT6tumor cells for 2 hours and the fluorescence of FITC from the cells wasdetected using laser scanning microscope.

Cell Viability Assays.

Tumor cells (1×104 per well) in 24-well tissue culture plates wereincubated with different combinations of SWNT and GC for 2 hours, rinsedwith PBS, and exposed to light at a fluence of 60-150 J/cm² (0.5-1.25W/cm² for 2 min). The light source was a 980-nm semiconductor laser.

Cell cytotoxicity in vitro was performed with a colorimetric tetrazoliumsalt-based assay, Cell Counting Kit-8 (CCK8). To detect photothermalcytotoxicity, tumor cells were irradiated by a 980-nm laser with orwithout incubation with SWNT-GC. OD450, the absorbance value at 450 nm,was read with a 96-well plate reader, to determine the viability of thecells.

Detection of TNFα.

To detect TNFα secretion by macrophages when stimulated by tumor cellsafter treatments, macrophages were incubated with treated tumor cells in24-well tissue culture plates. After 24 hours of incubation, thesupernatants were collected for ELISA detection.

Animal Tumor Model.

EMT6 cells (1×10⁶) in a 0.1-ml solution were injected into the flankregion of female Balb/c mice, aged 6-8 weeks. Animals were used inexperiments 7 to 10 days after tumor cell inoculation, when the tumorsreached a size of approximately 300 mm³.

Treatment of Animal Tumors Using Laser+SWNT-GC.

Tumor-bearing mice were divided into different treatment groups (12-16mice/group). A solution of 0.1-ml containing 5 mg/ml (25 mg/kg) GC or0.2 mg/ml (1 mg/kg) SWNT or 0.2 mg-5 mg/ml (1 mg-25 mg/kg) SWNT-GC wasdirectly injected into the center of each tumor, 2 hours beforeirradiation with a 980-nm laser. The light was delivered to the tumorusing a fiber optic delivery system. The power density at the treatmentarea, which encompassed the tumor and 0.5 to 1 cm of the surroundingskin, was 0.75 W/cm² for a treatment duration of 10 minutes. Duringlaser irradiation, mice were anesthetized with an intraperitonealinjection of pentobarbital sodium and were restrained in a speciallydesigned holder. After treatment, the mice were observed daily and thetumors were measured every other day for a period of 100 days.

Adoptive Immunity Transfer.

Mice successfully treated by Laser+SWNT-GC and Laser+SWNT werechallenged with an increased tumor dose of 2×10⁶ cells per mouse. At thesame time, control mice of the same age were inoculated with the samenumber of tumor cells. Twenty-eight days after the tumor inoculation,the mice were terminated by cervical dislocation, and their spleens weredissected free of fat. Spleen cell suspensions were prepared bymechanical disruption into medium with 10% FCS. Spleen cells and viabletumor cells were counted on a hemocytometer before admixed. Theadmixture had a 500:1 spleen to tumor cell ratio. Naive mice wereinoculated with a 0.2-ml admixture containing 5×10⁷ spleen cells and 10⁵tumor cells.

Seven days after treatment with different combinations of laser, SWNT,and GC, splenocytes from treated mice were cultured in the presence ofEMT6 tumor cells for 5 days, after which cell cytotoxicity was assessedwith CCK8.

Results

Characterization of SWNT-GC.

A stable SWNT-GC suspension was obtained after the final centrifugationof the solution. The schematic of SWNT-GC is given in FIG. 1A. The nearinfrared absorption spectra of SWNT-GC exhibit a strong band around 980nm (FIG. 1B), which is typical for CoMoCAT samples. The Roman spectra ofSWNT-GC is given in FIG. 1C. The optical absorbance of the GC solutionin this spectral window is extremely low.

The resonance ratio for the SWNT suspension in GC was measured to be0.140, which favorably compares to NaCholate (with a similar ratio of0.147), one of the best surfactants reported in literature. The SWNT-GCsuspension remained stable after storage for more than six months at 4°C.

Using SWNT-GC for light absorption enhancement, temperature increases ata depth of 4 mm below the surface of the gel phantom was measured bythermocouples. As shown in FIG. 2A, a 12° C. differential temperatureincrease was obtained between SWNT-GC enhanced gel and normal gel. Thesurface temperature increases of refrigerated samples are shown in FIG.2B. Under the same conditions, these increases demonstrate theselectivity of SWNT-GC at 980 nm. The temperature increase of the targetsample can be controlled by adjustment of the SWNT-GC concentration andlaser settings.

The temperature distributions inside a normal gel block, before andduring laser irradiation, obtained by magnetic resonance thermometry,are shown in FIGS. 3A and 3B. The temperature distribution inside theSWNT-GC enhanced gel block, before and during laser irradiation, areshown in FIGS. 3C and 3D. The results show a higher temperature increasein the SWNT-GC enhanced target.

To confirm that SWNT could carry GC into tumor cells, SWNT-GC wasfunctionalized with FITC, a fluorescent tag, and the fluorescenceemission from the tumor cell incubated with SWNT-GC-FITC or GC-FITC wasobserved. Confocal images of the EMT6 cells show that SWNT-GC-FITCaccumulates mainly in the cytoplasm, while GC-FITC is absent inside thecells (FIG. 4).

These results indicate that, as a unique quasi one-dimensional material,SWNT can carry GC into tumor cells, which fulfilled a crucial step fortemporally and spatially synchronized photothermal and immunologicalreactions in the target tumor cells under laser irradiation.

To determine the cytotoxicity of SWNT-GC under laser irradiation, EMT6tumor cells were incubated with the SWNT-GC solution for 2 hours,followed by irradiation with a 980-nm laser. Tumor cytotoxicity dependedon both the SWNT-GC concentration and the laser dose (FIG. 5).

In Vitro Immune Stimulation of SWNT-GC.

Immunological observations showed that GC and SWNT-GC stimulated asimilar level of TNFα secretion at a given concentration, when incubatedwith murine macrophages, and the level of TNFα secretion increased withGC concentration (FIG. 6A). These results showed that the stable SWNT-GCsuspension retained the immunological capability of GC.

To determine the immunological responses induced by treated tumor cells,ELISA was performed to measure TNFα secreted by macrophages incubatedwith tumor cells after different treatments for 24 hours. As shown inFIG. 6B, tumor cells incubated with either GC or SWNT-GC could stimulatea certain level of TNFα secretion, whereas a low dose laser irradiation(60 J/cm²) alone did not enhance the activation of macrophages. Tumorcells treated by higher doses of laser irradiation (120 or 150 J/cm²)also stimulated TNFα secretion by macrophages, due to laser induced celldeath. However, at these high light doses, tumor cells treated byLaser+SWNT-GC resulted in much higher levels of TNFα secretion (FIG.6B).

In Vivo Effects of SWNT-GC.

EMT6 cells were injected subcutaneously in the flank of Balb/c femalemice. After the tumor size reached approximately 300 mm³, the animalswere divided into eight different treatment groups. After treatment, themice were observed daily and the tumor volume was measured using acaliper every other day. The mice treated by injections of SWNT (1mg/kg, in PEG), GC (25 mg/kg), or SWNT-GC (1 mg-25 mg/kg) had an averagetumor burden similar to that of untreated control mice (FIG. 7A); noneof the mice in these three groups exhibited tumor regression. Incontrast, mice treated by laser irradiation (0.75 W/cm² for 10 min) hadan average tumor burden noticeably smaller than that of the control mice(FIG. 7B). Laser+SWNT and Laser+SWNT-GC treatments resulted insignificant tumor suppression (FIG. 7B).

For survival studies, sixteen mice were used per each treatment groupand the mice were monitored for 100 days after tumor inoculation. Amongmice treated by a single injection of SWNT, GC, or SWNT-GC solution,there were no long-term survivors, although mice in GC and SWNT-GCgroups had a slightly longer average survival time (FIG. 8A). Underlaser irradiation at a power density of 0.75 W/cm², the survival rateswere 100% in the Laser+SWNT-GC group, 56% in the Laser+SWNT group, 38%in the Laser+GC group, and 25% in the Laser only group, respectively(FIG. 8B). Nine of the sixteen mice in the Laser+SWNT group survived,but complete tumor regression was observed in only three mice, while nocomplete tumor regression was observed in the Laser+GC or the Laser onlygroups. Overall, the results in FIG. 8 demonstrate that theLaser+SWNT-GC combination is the most efficacious treatment, resultingin a much higher survival rate and stronger tumor suppression than othercombinations of laser, SWNT, and GC.

Rechallenge of the Cured Mice.

Mice successfully treated by Laser+SWNT-GC and Laser+SWNT werechallenged with 2×10⁶ viable tumor cells 100 days after the initialtumor inoculation (10 mice per group). Ten naive mice of the same agewere inoculated with 2×10⁶ viable tumor cells per mouse as controls. Asshown in FIG. 9, all the Laser+SWNT-GC cured mice showed totalresistance to the challenge. However, all the Laser+SWNT cured micedeveloped primary tumors and died within 80 days of tumor re-challenge.All the control mice developed primary tumors and died within 40 days oftumor inoculation. The Laser+SWNT-GC cured mice were challenged a secondtime with an increased tumor dose (3×10⁶/mouse). Again, they werecompletely refractory to the tumor rechallenge.

Adoptive Immunity Transfer.

Spleen cells from mice successfully treated by Laser+SWNT-GC orLaser+SWNT were harvested as immune cells. As controls, spleen cellsfrom untreated tumor-bearing mice were also collected. The spleen cellswere admixed with viable tumor cells at a ratio of 500:1. Naive micewere inoculated by 10⁵ viable tumor cells with 5×10⁷ spleen cellsharvested from mice of different treatment groups. FIG. 10 shows thesurvival rates of mice inoculated with the mixture of spleen cells andtumor cells. The spleen cells from Laser+SWNT-GC cured mice provided100% protection to the recipients, while the spleen cells fromLaser+SWNT cured mice protected only 30% of the recipients. The spleencells from control tumor-bearing mice provided only 10% protection tothe recipients (FIG. 10). Sixty days after adoptive immunity transfer,all the mice protected by the spleen cells from Laser+SWNT-GC-cured micewere challenged again with 2×10⁶ tumor cells; all mice withstood thesecond challenge.

Discussion

The ideal treatment modality for cancer, particularly metastatic cancer,should achieve a systemic, tumor-specific immunological response througha minimally invasive, local intervention. Such an approach couldpotentially suppress local tumors and at the same time eradicatemetastases at distant sites, while providing anti-tumor immunity to thehost with minimal adverse side effects. Photothermal reaction usinglasers is an ideal local intervention due to its precise energy deliveryto target tissue and the sensitivity of tumor tissue to temperatureincrease.

Laser light in the NIR region, in combination with appropriatelight-absorbing agents, is particularly attractive for selectivephotothermal interaction, because of the low absorbance of biologicaltissue in the NIR region.

SWNTs have been used as therapeutic targets to induce thermal injury tocancer cells. It has been shown that death of cancer cells withinternalized SWNTs could be induced by exposure to either continuous NIRlight or radiofrequency radiation.

Anti-tumor immune response can be significantly enhanced by introducingimmunological stimulants to the tumors, particularly when combined withother interventions. When used appropriately, such immunostimulants cansignificantly improve the efficacy of cancer treatment by stimulatingthe host immune system, such as when Corynebacterium parvum, bacilleCalmette-Gue'rin, or other immunoadjuvants were intratumorallyadministered in conjunction with phototherapy treatment.

SWNTs by CoMoCAT method are uniform in size and have a strong absorptionpeak around 980 nm, hence an ideal light-absorbing agent for the desiredselective photothermal interaction in local intervention. The selectivephotothermal laser-tissue interaction using the 980-nm laser and CoMoCATSWNT has been demonstrated through in vitro and in vivo experiments.

GC has also been used previously as an immunoadjuvant for cancertreatment in animal studies. The purpose of the proposed novel SWNT-GCsystem is to further improve the laser immunotherapy. The molecularstructures of CoMoCAT SWNTs and GC allow a stable, uniform SWNTsuspension using GC as an effective surfactant (FIG. 1). Theexperimental results clearly show that the SWNT-GC solution retained theoptical properties of SWNT (FIGS. 2 and 3) and the immunologicalproperties of GC.

The combination of SWNT-GC due to the electrical structure of both SWNTand GC also provides this novel system a unique advantage: carrying GCinto the tumor cells. Usually, immunological stimulants like glycatedchitosan, a long-chain polymer, cannot enter cells directly, asevidenced by the experimental results (FIG. 4, top panel). SWNT hasshown a capability to enter cells and localize in different subcellularcomponents depending on the molecules SWNT is carrying. When GC isconjugated with SWNT, it can be carried into tumor cells (FIG. 4, bottompanel). GC inside tumor cells can serve as exogenous immunologicalstimulant, hence further enhancing the immune responses induced by thecombined photothermal and immunological reactions by laser+SWNT-GC.

The advantage of the SWNT-GC system lies in its simultaneous,synergistic photothermal and immunological reactions during tumortreatment. Specifically, SWNT selectively absorbs the 980-nm laser lightto induce tumor cell destruction, hence providing an exogenous cellularstress and tumor immunogen to the host. In addition, GC enhances theimmune response at the same photothermal treatment site due to itsconjugation with SWNT. Therefore, because of the unique bound of SWNTand GC, they can target the same tumor cell at the same time, resultingin synergistic photothermal and immunological reactions.

The in vitro and in vivo results demonstrated the effectiveness ofLaser+SWNT-GC in the treatment of animal tumors.

While GC or SWNT-GC alone did not cause tumor cell death in vitro,combining with laser irradiation, particularly at higher doses (120 and150 J/cm²), they could significantly increase cytotoxicity (FIG. 5).Similarly, Laser+SWNT-GC treated tumor cells could induce much higherlevels of TNFα secretion from macrophages, as shown by the data in FIG.6. These results demonstrate the synergistic effect of laserirradiation, light absorption of SWNT, and immunological stimulation ofGC.

The synergy between laser, SWNT, and GC was further demonstrated by invivo experimental results, as shown in FIG. 7. Intratumoral injectionsof SWNT, GC, or SWNT-GC did not result in tumor regression (FIG. 7A),although treatments using single components with GC (GC or SWNT-GC)prolonged the medium survival time of the mice (FIG. 8A). These resultscould be attributed to the nonspecific immune response of host, inducedby GC, to enhance the tumor resistance, although such a response couldnot selectively destroy tumor cells, as evidenced by both in vitro (FIG.5) and in vivo (FIG. 7A) results. When laser irradiation was used, theeffect of SWNT-GC was significantly enhanced, both in vitro (FIG. 5) andin vivo (FIG. 7B). The treatment of Laser+SWNT-GC resulted in completetumor suppression, while the treatment of Laser+SWNT also resulted insignificant tumor suppression (FIG. 7B). Specifically, with a laserpower density 0.75 W/cm² and irradiation duration of 10 minutes, theLaser+SWNT-GC achieved a 100% cure rate, much higher than the cure rateof 56% with the Laser+SWNT treatment (FIG. 8B).

Mice successfully treated by Laser+SWNT-GC withstood subsequentchallenges with increased tumor dose; all the cured mice in this groupshowed total resistance to the tumor rechallenge (FIG. 9). However, themice successfully treated with the Laser+SWNT all developed primarytumors and died about 80 days after the tumor rechallenge (FIG. 9).These results demonstrate the essential role of GC in inducinglong-lasting anti-tumor immunity.

Splenocytes from mice cured by Laser+SWNT-GC provided 100% protection tonormal recipient mice when the animals were injected with a mixture ofthe spleen cells and tumor cells, as shown in FIG. 10. In comparison,splenocytes from mice cured by Laser+SWNT only provided partialprotection to the recipient mice (FIG. 10). These results indicate thatLaser+SWNT-GC induced a long-term memory in immune cells, again,attributed to the effect of GC.

It is hypothesized that the mechanism of Laser+SWNT-GC in the treatmentof tumors lies in the synergistic reactions between the selectivephotothermal reaction and immunological stimulation. The photothermalreaction reduces the tumor burden and at the same time exposes the tumorantigens; the immunoadjuvant in situ first stimulates the host immunesystem and then directs the immune system against the specific tumorcells. In each individual host, in fact, laser immunotherapy produced anin situ auto vaccine. This tandem effect not only resulted in totaltumor eradication but also led to a long-term tumor-specific immunity.This method, therefore, provides a systemic immunotherapy through localintervention for each individual host without the usually requiredimmune cross-reactivity.

In the present disclosure, an immunoadjuvant has been used as asurfactant to effectively disperse nanotubes to provide synergisticphotothermal and immunological effects under laser irradiation. Thissystem of the disclosure, due to its unique optical properties andimmunological functions, could be used in the treatment of tumors,particularly metastatic tumors. The system of the invention, due to thestrong binding of SWNT and GC, allowed GC being carried into the tumorcells, further enhancing the photothermal and immunological effects oflaser+SWNT-GC.

In summary, selective photothermal interaction and tumor-specificimmunological stimulation provided by Laser+SWNT-GC, whichsimultaneously target the tumor cells spatially and temporally, arecontemplated for use as an effective cancer treatment therapy.

Thus, the present invention is well adapted to carry out the objectivesand attain the ends and advantages mentioned above as well as thoseinherent therein. While presently preferred embodiments have beendescribed for purposes of this disclosure, numerous changes andmodifications will be apparent to those of ordinary skill in the art.

The invention claimed is:
 1. A method of photoimmunological therapy forinducing tumor cell destruction and anti-tumor immune responsescomprising: internalizing immunologically modified nanostructures in abody of the tumor cell in a host, said immunologically modifiednanostructures comprised of single-walled carbon nanotubes bound toglycated chitosan; exposing said tumor cell to either continuousnear-infrared light or radiofrequency radiation for providing thermaldamage or stress, thereby leading to death of the tumor cell andexposure of tumor antigens of said tumor cell to an immune system ofsaid host for promoting anti-tumor immune responses; wherein saidglycated chitosan solubilizes and stabilizes said nanotubes; whereinsaid steps of internalizing and exposing induce a synergistic, spatiallyand temporally synchronized photothermal-immunological anti-tumorresponse using the immunologically modified nanostructures as anexogenous light-absorbing agent and the immunological stimulant forimmune stimulation and activation.
 2. The method according to claim 1wherein: said single-walled carbon nanotubes are comprised of gold. 3.The method according to claim 1 wherein: said nanostructures have anabsorption peak in a range of 700 to 1500 nm.
 4. The method according toclaim 3 wherein: said nanostructures have an absorption peak with awavelength having a range of 800 to 1200 nm.
 5. The method according toclaim 1 wherein: said near-infrared light is produced by a 980-nm laser.6. The method according to claim 5 wherein: said near-infrared light isproduced by a laser having a laser power density in the ranges of 0.1 to5 W/cm², and administered with an irradiating duration of 5 to 60minutes.
 7. The method according to claim 6 wherein: said near-infraredlight is produced by a laser with a power density of 0.75 to 2 W/cm². 8.The method according to claim 6 wherein: said near-infrared light isadministered with an irradiating duration of 10 to 30 minutes.